I always thought you should not store a C02 pistol gassed because of the gas its self, not so.

Apparently it is because of the capsule itself leaving an imprint in the seal.

I have had an empty capsule in my Beretta for about six months( I know i should use it more) but i thought this would be OK as it was empty.

Needless to say i have taken it out now and put in a fresh one of a different make (the empty one was a Walther, new one Crossman) to check for leaks.
It seems OK, i will shoot this of tomorrow and never leave one in again.

All is explained
http://www.co2airguns.net/Collection...ders_Seals.htm

Although most of you probably know this already.